Two-way hydraulic unit



1969 L.. CARDWELL Two-WAY HYDBAULIC UNIT Filed April 15, 1968 United States Patent Oflce &483352 Paterted Dec. 16, 1969 3,483,952 Two-WAY HYDRAULIC UNIT lLloyd Cardwell, Barrington, Ill., assignor to Cardwell Westinghouse Company, a corporation of Delaware Filed Apr. 15, 1968, Ser. No. 721,314 1nt. Cl. F16d 57/06 US. Cl. 188-96 6 'Claims ABSTRACT OF THE DISCLOSURE A two-way hydraulic unit suitable for use in railroad car draft gears in which a piston or ram is slidably mounted in a closed cylinder with a rod extending from both sides of the ram through fluid seals in the ends of the cylinder. Centrally located in the ram is a metering pin which is maintained in neutral position by opposing coil springs. The metering pin Controls passageways to both sides of the ram so that one side of the passageways opens into the cylinder on one side of the ram and another set of passageways opens into the cylinder on the other side of the ram. Passageways connect the interior of the cylinder on each side of the ram. Each end of the metering pin is exposed to the pressure in the corresponding side of the cylinder so that when the ram is subjected to buff the pin will open in the one direction by virtue of the increase in pressure in the cylinder on one side of the ram, permitting controlled flow of hydraulic fluid from the high pressure to the low pressure side. When the hydraulic unit is subjected to pull or draft, the pin moves in the opposite direction and correspondingly opens the passageways connecting the other side of the cylinder so that there is controlled flow from the other side, which is now the high pressure side, to the opposite side of the cylinder. The cylinder walls may be formed with metering grooves to assist the metering pin in controlling passage of fluid from the high pressure to the low pressure side.

DESCRIPTION OF THE INVENTION It is well known in the art to provide double-acting hydraulic units with grooved walls which control the rate of flow of fluid from one side to the other side of the ram or piston member. The difliculty with this type of unit is that it is -unable to accommodate itself to different velocities of car impacts and different car weights. This invention provides a pressure sensitive element which enables the valve in the hydraulic unit to adjust to different velocities of car impact and different car weights. This is accomplished by providing a metering pin in the center of the ram or piston which is exposed to the hydraulic fluid on both sides of the ram. The metering pin Controls passageways that connect one side of the cylinder to the other side. The metering pin is held in its neutral position by opposite coil springs. Upon either application of bufi or draft to the cylinder unit, the metering pin will move to a position opening the passageways an amount correspondng to the pressure created by the force of the impact or pull. Grooves may be provided in the walls of the chamber as in conventional type units in order to provide additional fluid flow passageways during impact or buff.

DESCRIPTION OF THE DRAWINGS FIGURE l is a partially mutilated longitudinal, crosssectional View through the center of the hydraulic device in accordance with the invention.

FIGURE 2 is an enlarged, cross-section of a portion of the hydraulic device, along the line 2-2 of FIGURE 1, showing the valve structure of the hydraulic unit.

DETAILED DESCRIPTION Referring to the drawings, the numeral 1 indicates a cylinder made of suitable metal such as steel having a closed end 2 with oppositely extending hollow projection 3. The other end of the cylinder is closed by end cap 4 having hollow projection 5. The end cap 4 is fastened to the cylinder by means of bolts 6 threaded into tapped holes in the cylinder end, in fluid tight relation therewith. Mounted within the cylinder or chamber 1 is a ram or piston 7 having piston ring 9 to provide for substantially leak-proof contact between the periphery of the piston and the inside cylinder wall. The piston 7 is preferably formed integrally with solid piston rod 11 extending through projection 3 and maintained in leak-proof relationship with the internal walls of projection 3 by means of sealing rings 13. A second piston rod 15 of same crosssection as rod 11 is threaded onto the opposite side of piston 7 by means of threads 17 and extends through projection 5 and is maintained in leak-proof relation to the inside walls thereof by means of sealing rings 19. Although either rod 11 or 15 may be suitably connected to a coupler so as to impose both bufi and draft forces on the hydraulic unit, it is preferred to connect to rod 11 which is formed inte grally with the piston.

Piston 7 is formed with two diagonal passageways 21 extending from a central chamber 22 of the piston through the face 23 thereof, in contact with the left side of cylinder chamber 24. Two other passageways 25 eXtend diagonally from the central chamber 22 of piston 7 to the face 26 of piston 7 which is in contact with the right-hand side of cylinder chamber 24. The aXes of passageways 25 preferably lie in a plane at right angles to the plane passing through the axes of passageways 21. The centers of the inner ends or orifices 28 of passageways 21 and 25 preferably lie in a plane parallel to the side walls or faces 23 and 26 of piston 7.

Within chamber 22 a metering pin 27 is snugly and reciprocally mounted. Col springs 29 and 31, which are normally under partial compression, bias metering pin 27 in opposite directions to normally maintain it in neutral position closing passageways 21 and 25. Metering pin 27 is formed with oppositely extending stems 33 and 35 which snugly t in axial bores 37 and 39 of piston rods 15 and 11, respectively. The stems 37 and 39 are adapted to reciprocate in the bores. A transverse bore 41 through piston rod 15 communicates the left-hand side of chamber 24 with axial bore 37 and a transverse bore 43 through piston rod 11 communicates the right-hand side of chamber 24 with axial bore 39.

Metering pin 27 is fonned with one or more small bores 45 extending through the pin from one side to the other. The bores 45 equalize pressure on the two sides of the pin to prevent pressure build-up on either side of the metering pin which might otherwise occur because of leakage of fluid past the stems 33 and 35.

One or more tapering grooves 47, and preferably four equally spaced grooves, decreasing in cross-section from the end 43 to the opposite end may be provided in the inner cylinder wall to provide additional cushioning during impact. Such grooves are well known and are mathematically calculated to produce optimum conditions of maximum energy absorption with minimum force. Instead of tapering the grooves from the center of the cylinder toward each end as done in U.S. P atent No. 3,163,30O to J. C. Settles, the grooves taper from a maximum starting at a locus about one-fourth the distance to one end and three-fourths the distance to the other end, to zero at the end farthest from the starting locus. The starting locus 48 also is the neutral or starting point for the piston 7. Thus the maximum piston travel on buff is approximately three to four times the maximum piston travel on pull or draft.

The operation of the device is as follows:

Assume that the device is subjected to bufl? caused by impact against the end of piston rod 11. The impact will cause piston 7 to move to the left increasing the pressure in the left-hand side of cylinder 1. The increased pressure is communicated to the end 33 of pin 27 through transverse passage 41. When the pressure is sufficiently great to overcome spring 31, metering pin 27 will move to the right, opening passageways 21 and 25. The extent to which the passageways are opened will depend upon the force of the impact, thereby automatically adjusting for weight and velocity of the impacting body. As soon as the pin 27 opens the passageways 21 and 25, hydraulic fluid will flow from the left-hand high pressure side to the right-hand low pressure side of the cylinder. The area of orifice opening will depend on the difference in pressure between the fluid pressure on end of pin 33 and pin 35, and the resistance to compression of spring 31. In this way the area of the orifice opening is directly related to the pressure in the high pressure side of cylinder 24. The greater the pressure the larger the opening. In this way, the metering valve is pressure sensitive, adjusting itself to higher velocities or greater bodies of mass. The last case might occur when two or more cars are impacted into a string of cars. This pressure sensitive feature also acts as a safety valve, preventing breakage of the unit under extremely high Velocity impacts. Since both piston rods are alike, no additional storage is needed for hydraulic fluid as it is displaced from either side of the cylinder into the other side.

Hydraulic fluid will also flow during impact through metering grooves 47 to assist in buflering loads during impact.

When the hydraulic unit is subjected to pull, it works in the opposite direction. With a pulling force on rod 11 of suflicent magnitude, the piston 7 moves to the right, creating pressure in the right-hand side of cylinder chamber 24. This pressure is communicated through transverse passage 43 to the end of stern 35, causing the metering pin 27 to move to the left, thereby opening the orifices 28 to passageways 21 and 25 so that fluid can flow from the right-hand side of chamber 24 through passageway 21 to the left-hand or low pressure side of cylinder chamber 24. During pull the piston travels a relatively short distance as compared to travel during bufr'. Moreover, the portion of the cylinder traveled by the piston during pull has no metering grooves in the cylinder wall. The metering grooves are left out in order to prevent the unit from creeping open or closed in train action which is a common fault found in other metered hydraulic devices.

The two-way hydraulic unit here described is adapted to be mounted at the end of a railroad car in a suitable center sill with the cylinder rigidly mounted in the sill adjacent one end thereof and with one piston rod, preferably the one integral with the piston, suitably attached to a coupling device that is capable of exerting both buff and draft on the rod.

suitable spring means will be provided to restore the piston 7 to its neutral or starting position opposite ends 48 of grooves 47 upon dissipation of the draft or buff force mposed on the device.

Although the pin 21 should fit snugly within the chamber 22 and the stems 33 and 35 should fit snugly within the bores 37 and 39, it is not necessary that they be in leak-proof relation to the respective walls of the chambers and bores, since the small passageways 45 are provided to equalize pressure on the two faces of the pin 27 so that pressure cannot build up on one or the other faces of the pin. Preferably, a number of passageways 45 are provided in a circular pattern so as to provide easy flow of fluid from one side to the other of the pin 27.

The area of the ends of the stems 33 and 35, the tension of the springs 29 and 31, and the relationship between the orifices to p-assages 21 and 25 and of the pin 27 are calculated so as to Correlate the size of the opening of the orifices with the pressure produced by the bull or impact on the device.

Although the two-way hydraulic device just described is suitable generally for any purposes where it is desired to buffer against forces in two opposite directions, the device is particularly adapted for use as an end-of-car cushioning device for ralroad cars to provide against excessive Shock to lading caused by impact and by draft or pull forces, which occur particularly When cars are being started from a standing position.

I claim:

1. A two-way hydraulic unit comprising a closed, nonexpandable cylinder, a re'ciprocal piston supported in said cylinder dividing said cylinder into first and second chambers, piston rods of substantially identical cross-sectional area attached to opposite sides of said piston and extending through opposite ends of said cylinder, a third chamber in said piston, a metering pin slidably mounted in said third chamber, at least one passageway in said piston connecting said third chamber to said first chamber, at least one passageway in said piston connecting said third chamber to said second chamber, said passageways being the only substantal communication between said third chamber and said first and second chambers, an orifice at one end of each said passageway, the extent of opening ot' which is controlled by said pin, connecting said third chamber to each said passageway at loci such that said metering pin functions as a closure for said orifices when the pin is in neutral position and functions to simultaneously open said orifices a variable amount, depending on pressure in said first and second chambers when said metering pin is biased in either direction, opposing resilient springs biasing said metering pin to normally retain it in neutral position, separate conduit means for applying fluid pressure from said first chamber to one end of said metering pin in a direction opposite to the bias of one of said resilient means, and separate conduit means for applying fluid pressure from said second chamber to the opposite end of said metering pin in a direction opposite to the bias of the other of said resilient means.

2. A two-Way hydraulic unit in accordance With claim 1 in which the inner wall of said cylinder is provided with at least one metering groove to enable fluid to pass from the high pressure to the low pressure side of said cylinder between the piston and inner cylinder wall.

3. A two-way hydraulic unit in accordance with claim 1 in which said metering pin is formed with a central enlarged portion snugly mounted in said third chamber and stems extending from opposite sides of said enlarged portion, said stems being snugly and reciprocatively mounted in axial bores in said piston rods, said bores providing a portion of said conduit means for applying fluid pressure to the metering pin from said first and second chambers.

4. A two-way hydraulic unit in accordance with claim 3 in which the means for applying fluid pressure from said first and second chambers to said metering pin includes transverse bores in said piston rods connecting with said axial bores.

5. A two-way hydraulic unit in accordance with claim 3 in which said central enlarged portion has at least one unobstructed passageway therethrough communicating with said third chamber on both sides of said enlarged portion, such unobstructed passageways being of smaller cross-sectional area than the aforesaid passageways.

6. A two-way hydraulic unit in accordance with claim 5 in which said opposing resilient sprngs are coil springs 6 surrounding said stems within said third chamber on each FOREIGN PATENTS side of said central enlarged portion. 1,096528 2/1955 France.

References Cited 716,726 1/1942 Germany.

UNITED STATES PATENTS 5 GEORGE E. A. HALVOSA, Primary EXaminer 2 771968 11/1956 Mercier 137-493 X y U.S. Cl. X.R. 2,937,724 5/1960 Schntzer. 137 213 43 3,275,164 9/1966 Peterson 273-43 

